Monocrystalline silicons with a low electrical resistivity have recently been demanded. In a known manufacturing method of such monocrystalline silicons, according to which an n-type dopant is densely added, single crystallization is sometimes hampered, and thus studies have been conducted on prevention of such a problem (see, for instance, Patent Literature JP 2008-297167 A).
Patent Literature 1 discloses that addition of a large amount of the dopant significantly increases a freezing-point depression to cause compositional supercooling, and an abnormal growth (Cell growth), which is different from a silicon growth on a silicon growth face, is induced on a crystal growth interface when such compositional supercooling is large to hamper single crystallization.
According to the manufacturing method of Patent Literature 1, which takes into account that a temperature gradient in a silicon melt cannot be directly measured, a monocrystalline silicon is manufactured in such a manner that a predetermined relationship is satisfied between a temperature gradient of the monocrystalline silicon, which is used in place of the temperature gradient in the silicon melt, a dopant concentration in the silicon melt, a pull-up speed, and a coefficient corresponding to a dopant type.
However, dislocation sometimes occurs at an early stage of crystal growth in the process of manufacturing the monocrystalline silicon to hamper single crystallization, proving that the method of Patent Literature 1 cannot always prevent the problem.